docs: def insert(self, value):
          """Insert a value in the tree"""
          if not self.payload or value == self.payload:
              self.payload = value
          else:
              if value <= self.payload:
                  if self.left:
                      self.left.insert(value)
                  else:
                      self.left = BinaryTreeNode(value)
              else:
                  if self.right:
                      self.right.insert(value)
                  else:
                      self.right = BinaryTreeNode(value)